Epoxy-containing compounds are known to be curable using various cationic initiator systems.
E.g. Smith, U.S. Pat. No. 4,256,828, describes photopolymerizable compositions that contain epoxides, an organic compound with hydroxyl functionality, and a photosensitive aromatic sulfonium or iodonium salt of a halogen containing complex ion.
Hayase et al., U.S. Pat. No. 4,835,193, describe photopolymerizable epoxy resin compositions that comprise an epoxy resin and a heteropoly-acid aromatic sulfonium salt as the photocuring catalyst.
In WO 95/14716 Neckers et al. describe photohardenable compositions that comprise a cationically polymerizable compound, a xanthene or fluorone dye, a hydrogen donor, and an onium salt.
Palazzotto et al., U.S. Pat. No. 5,545,676, describe addition polymerization of free-radically polymerizable materials. The disclosed photoinitiator system comprises an aryliodonium salt, a sensitizer, and an electron donor having an oxidation potential less than or equal to that of p-dimethoxybenzene.
Oxman et al., U.S. Pat. No. 6,025,406, U.S. Pat. No. 6,043,295, U.S. Pat. No. 5,998,495 and U.S. Pat. No. 6,187,833 describe a ternary photoinitiator system for curing of epoxy resins.
Weinmann et al., U.S. Pat. No. 6,084,004, describe compositions that undergo cationic curing and comprise a diaryliodonium compound, an alpha-dicarbonyl compound, a compound containing epoxide and/or oxetane groups, and an aromatic amine.
Especially for visible light cationically curing compositions a ternary photoinitiator system consisting of a sensitizer (e.g. a 1,2-diketone like e.g. camphorquinone (CQ)), a so-called electron donor (e.g. polycyclic aromatic compounds like e.g. anthracene and/or derivatives thereof), and an acid generator (i.e. a latent Lewis and/or Broensted acid like e.g. an iodonium salt as proton generator) is used. Such systems are described e.g. in WO 03/059295 and WO 05/051332.
For visible light cationically curing dental compositions a ternary photoinitiator system consisting of a sensitizer (e.g. camphorquinone), an electron donor (e.g. anthracene) and an acid generator (e.g. diaryliodonium salt) overall show good performance.